The invention relates to a method for optimizing a rinsing phase in a washing machine comprising a program control system for controlling the sequence of a program, a drum which is rotatably mounted in an outer tub, a water feed system, a dispensing drawer, a liquor outlet system arranged at the base of the outer tub with a drain pump, a drive motor for the drum and a sensor for the presence of fabric softener in a rinsing liquid situated in the outer tub, wherein the rinsing phase comprises at least one first step and one last step, and also relates to a washing machine which is particularly suitable for carrying out said method.
It is known to detect contaminants or particles and washing agent dissolving processes by means of an optical sensor in a washing machine.
DE 196 50 915 B4 discloses a domestic appliance operating with liquid and having a program control system and a conductance sensor by means of which the conductance of a liquid situated in the active region of the domestic appliance can be determined, wherein using the results from the conductance measurement, a cleaning substance contained in the liquid can be identified and, depending on the conductance detected and the cleaner type identified, a pre-defined program is carried out.
EP 0 649 933 B1 discloses a washing machine with controlled washing agent usage and a control method. The washing machine includes means for detecting the washing agent concentration in the washing liquid and means for estimating the optimum washing agent concentration and means which display to the user the results of the comparison of the washing agent concentration detected with the estimated optimum washing agent concentration.
DE 103 47 766 A1 discloses a domestic appliance which is able to carry out a cleaning procedure using cleaning liquid, having a system for feeding cleaning agent into the cleaning liquid. A sensor determines the content of active washing substances in the cleaning liquid during the cleaning procedure. A dosing system is also present which, if the content of active washing substances is too low, feeds additional cleaning agent or, if the content of active washing substances is too high, feeds fresh water into the cleaning liquid. Preferably, the sensor is a surfactant sensor which determines the surfactant content in the cleaning fluid by means of a bubble pressure method.
From DE 195 29 787 A1 a method for fill level-independent determination of the surface tension of liquid substances is known which is preferably suitable for determining and influencing the quality of liquors during washing and/or rinsing of soiled or clean textile goods. For this purpose, a gaseous stream is fed into the liquid to be measured and the bubble pressure and/or the flow rate is measured and evaluated during bubble bursting.
DE 100 42 846 A1 discloses a method for qualitative and/or quantitative characterization of polar components in liquids by impedance measurement and the use of the method and possibly an electrode arrangement for controlling the surfactant feed based on the characterization of the surfactant content in the washing water and/or rinsing water of washing machines.
DE 10 2007 041 069 A1 describes a method for recognizing fabric softener in a washing machine with program control for controlling a program sequence, a drum which is rotatably mounted in an outer tub, a water feed system, a liquor outlet system arranged at the base of the outer tub with a drain pump, a drive motor for the drum and a sensor, wherein in a washing procedure, following a washing or rinsing step, particularly following a rinsing step with clean water, a signal is detected from the sensor and is evaluated by comparison with a reference signal with respect to the presence of fabric softener. Depending on the quantity of fabric softener detected, the duration of the softening step and/or further subsequent rinsing steps, the temperature of the rinsing liquid, the rotational speed of the drum etc. can be determined.
DE 3907357 discloses a method for rinsing washing in a program-controlled drum washing machine in a plurality of sequential rinsing operations, wherein the last rinsing operation is performed with an increased rinsing water quantity compared with the preceding rinsing operations and the increased rinsing water quantity is let in for the last rinsing operation only if a fabric softener is used.
EP 1 184 505 A2 discloses a method for controlling a washing program in a washing machine, in particular a domestic washing machine, comprising a measuring device for determining the washing agent concentration of the washing liquor or rinsing liquor situated in an outer tub, wherein the washing program comprises at least the program sections of washing and rinsing. A control device stores the washing agent concentration values detected in the washing program section and determines, depending thereon, the sequence of the rinsing program section with respect to the number and/or duration of individual rinsing operations and/or the rinsing water quantity fed into the outer tub.
A washing program usually involves, following the actual washing step and at least one rinsing step in which only water is used as the rinsing liquid to rinse out any remaining washing agent, at the wish of the user, a rinse with a fabric softener. The dosing of fabric softener into the liquid is usually carried out by adding an empirical or prescribed quantity of fabric softener. For the calculation of an optimum concentration of fabric softener, the dependence thereof on a plurality of factors such as the temperature and the hardness of the water as well as the type and quantity of the washing need to be taken into account. The duration of the fabric softener rinse also depends on the quantity of fabric softener used.
An object of the present invention is therefore to provide a method for further improving a rinsing phase in a program-controlled washing machine and a programmable washing machine that is suitable therefor.
This object is achieved according to the invention with a method for optimizing a rinsing phase in a washing machine having the features of the corresponding independent claim and the washing machine of the corresponding independent claim. Preferred embodiments of the method according to the invention and of the washing machine according to the invention are disclosed in corresponding dependent claims. Preferred embodiments of the method according to the invention correspond to preferred embodiments of the washing machine according to the invention and vice versa, even if not explicitly stated herein.
The subject matter of the invention is therefore a method for optimizing a rinsing phase in a washing machine comprising program control for controlling a program sequence, a drum which is rotatably mounted in an outer tub, a water feed system, a dispensing drawer, a liquor outlet system arranged at the base of the outer tub with a drain pump, a drive motor for the drum and a sensor for the presence of fabric softener in a rinsing liquid situated in the outer tub, wherein the rinsing phase comprises at least one first step and one last step, and in which method in the last step, alternatively a rinsing step with water only and a rinsing step with water and fabric softener are provided, that in the last step, a rinsing liquid is let into the outer tub and a signal from the sensor is detected, said signal is evaluated by comparison with a reference signal SRef with respect to the presence of fabric softener in the rinsing liquid, that if the presence of fabric softener is not detected, the rinsing step with water only takes place, that if the presence of fabric softener is detected, the rinsing step with water and fabric softener takes place, and that in the rinsing step with water and fabric softener, compared with the rinsing step with water only, a washing kinetics is understood to mean the input of mechanical energy into the washing items to be treated in the drum, and the washing kinetics WM1 is reduced by at least 15%, wherein the washing kinetics WM comprises a switch-on time [in %], a duration of a reversing cycle [in s] and a rotational speed [in rpm] of the drum, wherein the switch-on time [%] and the rotational speed [rpm] of the drum are each reduced by at least 20% and the duration of a reversing cycle [s] is increased by at least 20%.
The washing kinetics is generally understood to mean the input of mechanical energy into the washing items to be treated in the drum, particularly the items to be washed or rinsed. According to the invention, the washing kinetics WM comprises a switch-on time [in %], a duration of a reversing cycle [in s] and a rotational speed [in rpm] of the drum. If the presence of fabric softener is detected, the switch-on time [in %] and the rotational speed [in rpm] of the drum are each reduced by at least 20%, preferably by at least 50% and the duration of a reversing cycle [in s] is increased compared with the first clean water rinsing step by at least 20%, preferably by at least 50%.